GASTROBOLETUS SUBALPINUS Trappe and Thiers, Brittonia 21:245. 1969

Illustrations: See Microfiche No. 25

Gastrocarp 6-10 cm broad, convex, becoming plane to deeply depressed to plano-convex at maturity, frequently highly pitted and wrinkled and irregular in outline; surface dry to moist, glabrous to velutinous to subtomentose, typically covered with adherent soil and debris; color when young pale tan ("warm buff" to "light buff" to "pale olive-buff" to "pinkish cinnamon"), unchanging with age or darkening to near pale brown ("clay color" to "buckthorn brown"), peridium on lateral and undersides of gleba white, thin, velvety, persistent except for scattered, circular ruptures over mouths of occasional glebal tubes in age. Context 0.3-1.5 cm thick at disc, soft, white or sometimes with sordid yellowish to olivaceous zones, in some slowly staining pinkish to grayish lavender when cut. Odor mild to farinaceous; taste mild, pleasant.

Gleba tubulose, the tubes 1-3 cm long, but markedly diminished in length in both directions from the broadest point of the hymenophore; grayish yellow ("dark olive-buff" to "pale olive-buff"), with age becoming olive brown ("buffy citrine" to "citrine-drab"). Gleba depressed to free from stipe-columella, strongly projecting beyond upper peridium but then covered by the thin, pallid, lateral peridium. Tubes occasionally oriented vertically near the stipe-columella, but mostly curved and oriented 20 degrees from vertical to horizontal, or angled upward near edges of the hymenophore; pores small, less than 1 mm broad, concolorous with tubes, unchanging when bruised.

Stipe-columella 2-5 cm long, 2-4.5 cm thick at apex, subventricose or tapering downward, occasionally equal to bulbous at the base, base up to 3-4 cm broad in some gastrocarps; surface dry, but typically covered with adherent soil and debris, glabrous to velutinous to subtomentose with the apex reticulate when the gleba has seceded; color dirty white to tan ("warm buff" to "light buff"), in some the base orange yellow ("apricot yellow"). Context white, unchanging.

Spores 10-16(18) X 4.5-6(8) Ám, smooth, ellipsoid, oblong to subovate, occasionally irregularly constricted near middle, light yellow to ochraceous in KOH and Melzer's, moderately thick-walled, sterigmal appendages oblique.

Basidia 40-48 X 8-13 Ám, thin-walled, hyaline and guttulate in KOH, clavate, with four sterigmata, 3-4 Ám long. Hymenial cystidia 24-75 X 7-10 Ám, often abundant when young, especially on the pores, apparently collapsing with age, single or sometimes clustered, hyaline in KOH and Melzer's, thin-walled, subcylindric to clavate to tapered.

Tube trama 60-80 Ám wide, consisting of hyaline, parallel hyphae 4-6(8) Ám wide. Peridial trama of thin-walled, often inflated, loosely interwoven hyphae (3)8-25 Ám wide, hyaline laticiferous hyphae 12-20 Ám wide with walls thickened to 1Ám scattered throughout. Peridial cuticle on upper surface of gastrocarp composed of closely interwoven, much branched hyphae 4-15 Ám wide, with erect, tapered, blunt-tipped terminal cells 25-45 X 7-12 Ám, sparsely scattered over the surface, hyaline in KOH, in Melzer's pallid to pale yellow to bright reddish brown, with darkly colored areas having intercellular deposits of dextrinoid debris. Peridial cuticle over lateral and undersides of gleba when young a trichodermium of blunt-tipped, cylindric to tapered to occasionally subcapitate cells 27-65 X 8-12 Ám, collapsing with age. Cuticle of stipe-columella when young a palisade of hyaline clavate cells 22-35 X 6-15 Ám, with occasional fertile basidia, collapsing with age. Clamp connections absent.

Habit, habitat, and distribution Solitary to gregarious, hypogeous or partially erumpent, under and probably mycorrhizal with pines and firs and possibly other conifers of montane and subalpine forests. Commonly found in late spring and summer.

Material studied Calaveras County: Thiers 21266, 21270. Fresno County: Thiers 13422, 13436. Sierra County: Thiers 21151, 23955, 23956, 23647. Tuolumne County: Thiers 21017, 21071, 21292.

Observations Gastroboletus subalpinus is readily distinguished from the other known species of the genus by its smooth, generally whitish pallid peridium and stipe. It is distinctly gastroid in having a gleba whose tubes are not vertically oriented, and mostly covered by peridial tissue through maturity. When first collected in California, the specimens were thought to be abnormal basidiocarps of Boletus edulis, although the tubes were more or less enclosed and disorganized in orientation. Subsequent collections made it apparent, however, that these were basidiocarps of a species of Gastroboletus. In the case of each collection, careful search was made for normal -appearing basidiocarps of B. edulis, but none was found.

Edibility undetermined.

The Boletes of California
Copyright © 1975 by Dr. Harry D. Thiers
Additional content for the online edition © 1998 by Michael Wood, Fred Stevens, & Michael Boom
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